1. Field of Invention
The invention relates to wireless communications, and more specifically to a wireless communication device that is capable of efficiently measuring a secondary radio access technology.
2. Related Art
Wireless communication devices, such as cellular telephones to provide an example, are becoming commonplace in both personal and commercial settings. The wireless communication devices provide users with access to all kinds of information, as well as the ability to communicate with other such devices across large distances. For example, a user can access the internet through an internet browser on the device, download miniature applications (e.g., “apps”) from a digital marketplace, send and receive emails, or make telephone calls using a voice over internet protocol (VoIP). Consequently, wireless communication devices provide users with significant mobility, while allowing them to remain “connected” to communication channels and information.
Wireless communication devices communicate with one or more other wireless communication devices or wireless access points to send and receive data. Typically, a first wireless communication device generates and transmits a radio frequency signal modulated with encoded information. This radio frequency signal is transmitted into a wireless environment and is received by a second wireless communication device. The second wireless communication device demodulates and decodes the received signal to obtain the information. The second wireless communication device may then respond in a similar manner. The wireless communication devices can communicate with each other or with access points using any well-known modulation scheme, including simple amplitude modulation (AM), simple frequency modulation (FM), quadrature amplitude modulation (QAM), phase shift keying (PSK), quadrature phase shift keying (QPSK), and/or orthogonal frequency-division multiplexing (OFDM), as well as any other communication scheme that is now, or will be, known.
Different wireless communication devices may communicate using any one of different radio access technologies (RATs), including WiMAX, LTE, 4G, 3G, 2G, and WiFi, among others. Some devices are capable of communicating using multiple different RATs. At any given time, a multi-RAT device can be currently communicating using a primary RAT, while measuring signals from one or more secondary RATs that the device is not currently utilizing, but may utilize in the future if conditions warrant. The measurements for the secondary RAT occur only during time periods allocated for measurement gaps that are provided by the primary RAT.
As a result of this measurement scheme, the performance of current devices suffers. Specifically, measurement gaps provided for the primary RAT may be insufficient to measure the secondary RATs. For example, 2G measurement gaps are approximately 4.6 ms. However, 4G measurements typically require 5-6 ms. As a result, in order to perform the 4G measurement, current devices must ignore several of the incoming 2G packets that follow the 2G measurement gap in order to complete the 4G measurement. This can result in erroneous signals and/or reduced throughput through retransmission of the ignored signal.
In addition, when performing a handoff from the primary RAT to a secondary RAT, typical devices must again acquire the measurements from the secondary RAT. This handoff measurement is performed after communications with the primary RAT have ceased, which significantly adds to handoff preparation time, and therefore increases handoff latency.
Consequently, there is a need for a wireless communication device capable of efficiently performing measurements of secondary RATs. Further aspects and advantages of the invention will become apparent from the detailed description that follows.
The invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.